#include "OSCBase64.h"

unsigned char *OSC_base64_encode(unsigned char *str, long str_len)
{
    long len;
    unsigned char *res;
    int i, j;
    /* 定义base64编码表 */
    const char *base64_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

    if (str_len % 3 == 0)
    {
        len = str_len / 3 * 4;
    }
    else
    {
        len = (str_len / 3 + 1) * 4;
    }

    res = malloc(sizeof(unsigned char) * len + 1);
    res[len] = '\0';

    /* 以3个8位字符为一组进行编码 */
    for (i = 0, j = 0; i < len - 2; j += 3, i += 4)
    {
        /* 取出第一个字符的前6位并找出对应的结果字符 */
        res[i] = base64_table[str[j] >> 2];
        /* 将第一个字符的后位与第二个字符的前4位进行组合并找到对应的结果字符 */
        res[i + 1] = base64_table[(str[j] & 0x3) << 4 | (str[j + 1] >> 4)];
        /* 将第二个字符的后4位与第三个字符的前2位组合并找出对应的结果字符 */
        res[i + 2] = base64_table[(str[j + 1] & 0xf) << 2 | (str[j + 2] >> 6)];
        /* 取出第三个字符的后6位并找出结果字符 */
        res[i + 3] = base64_table[str[j + 2] & 0x3f];
    }

    switch (str_len % 3)
    {
    case 1:
        res[i - 2] = '=';
        res[i - 1] = '=';
        break;
    case 2:
        res[i - 1] = '=';
        break;
    }

    return res;
}

unsigned char *OSC_base64_decode(unsigned char *code)
{
    /* 根据base64表，以字符找到对应的十进制数据 */
    int table[] = {
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 62, 0, 0, 0,
        63, 52, 53, 54, 55, 56, 57, 58,
        59, 60, 61, 0, 0, 0, 0, 0, 0, 0, 0,
        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
        13, 14, 15, 16, 17, 18, 19, 20, 21,
        22, 23, 24, 25, 0, 0, 0, 0, 0, 0, 26,
        27, 28, 29, 30, 31, 32, 33, 34, 35,
        36, 37, 38, 39, 40, 41, 42, 43, 44,
        45, 46, 47, 48, 49, 50, 51};
    long len;
    long str_len;
    unsigned char *res;
    int i, j;

    /* 计算解码后的字符串长度 */
    len = strlen((char *)code);
    /* 判断编码后的字符串后是否有= */
    if (strstr((char *)code, "=="))
    {
        str_len = len / 4 * 3 - 2;
    }
    else if (strstr((char *)code, "="))
    {
        str_len = len / 4 * 3 - 1;
    }
    else
    {
        str_len = len / 4 * 3;
    }

    res = malloc(sizeof(unsigned char) * str_len + 1);
    res[str_len] = '\0';

    /* 以4个字符为一位进行解码 */
    for (i = 0, j = 0; i < len - 2; j += 3, i += 4)
    {
        /* 取出第一个字符对应base64表的十进制数的前6位与第二个字符对应base64表的十进制数的后2位进行组合 */
        res[j] = ((unsigned char)table[code[i]]) << 2 | (((unsigned char)table[code[i + 1]]) >> 4);
        /* 取出第二个字符对应base64表的十进制数的后4位与第三个字符对应bas464表的十进制数的后4位进行组合 */
        res[j + 1] = (((unsigned char)table[code[i + 1]]) << 4) | (((unsigned char)table[code[i + 2]]) >> 2);
        /* 取出第三个字符对应base64表的十进制数的后2位与第4个字符进行组合 */
        res[j + 2] = (((unsigned char)table[code[i + 2]]) << 6) | ((unsigned char)table[code[i + 3]]);
    }

    return res;
}

unsigned char *OSC_base64_decode_outlen(unsigned char *code, long *out_len)
{
    /* 根据base64表，以字符找到对应的十进制数据 */
    int table[] = {
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 62, 0, 0, 0,
        63, 52, 53, 54, 55, 56, 57, 58,
        59, 60, 61, 0, 0, 0, 0, 0, 0, 0, 0,
        1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
        13, 14, 15, 16, 17, 18, 19, 20, 21,
        22, 23, 24, 25, 0, 0, 0, 0, 0, 0, 26,
        27, 28, 29, 30, 31, 32, 33, 34, 35,
        36, 37, 38, 39, 40, 41, 42, 43, 44,
        45, 46, 47, 48, 49, 50, 51};
    long len;
    long str_len;
    unsigned char *res;
    int i, j;

    /* 计算解码后的字符串长度 */
    len = strlen((char *)code);
    /* 判断编码后的字符串后是否有= */
    if (strstr((char *)code, "=="))
    {
        str_len = len / 4 * 3 - 2;
    }
    else if (strstr((char *)code, "="))
    {
        str_len = len / 4 * 3 - 1;
    }
    else
    {
        str_len = len / 4 * 3;
    }

    res = malloc(sizeof(unsigned char) * str_len + 1);
    res[str_len] = '\0';
    *out_len = str_len;

    /* 以4个字符为一位进行解码 */
    for (i = 0, j = 0; i < len - 2; j += 3, i += 4)
    {
        /* 取出第一个字符对应base64表的十进制数的前6位与第二个字符对应base64表的十进制数的后2位进行组合 */
        res[j] = ((unsigned char)table[code[i]]) << 2 | (((unsigned char)table[code[i + 1]]) >> 4);
        /* 取出第二个字符对应base64表的十进制数的后4位与第三个字符对应bas464表的十进制数的后4位进行组合 */
        res[j + 1] = (((unsigned char)table[code[i + 1]]) << 4) | (((unsigned char)table[code[i + 2]]) >> 2);
        /* 取出第三个字符对应base64表的十进制数的后2位与第4个字符进行组合 */
        res[j + 2] = (((unsigned char)table[code[i + 2]]) << 6) | ((unsigned char)table[code[i + 3]]);
    }

    return res;
}
